Injection syringe with mobile needle guard

ABSTRACT

The injection syringe has at least one syringe body ( 12 ) provided with a needle ( 22 ) and a pusher (14) mounted so as to be able to move in the body ( 12 ). The syringe has a movable guard ( 36 ) for protecting the injection end ( 22 A) of the needle. The guard ( 36 ) is able to move with respect to the body ( 12 ) between a position retracted in the body ( 12 ) and an active protection position. The guard ( 36 ) and the body ( 12 ) have associated projecting and recessed reliefs for holding the guard in a retracted position. It has a retractable member ( 70 ) for positive holding of the engagement of the said associated reliefs, when the guard ( 36 ) is in a retracted position. The pusher ( 14 ) and the said holding member ( 70 ) are adapted for a retraction of the said holding member ( 70 ) under the action of the pushing in of the pusher ( 14 ) into the body, at the end of injection, providing a release of the positive holding of the engagement of the associated reliefs.

[0001] The present invention concerns an injection syringe of the typehaving a syringe body provided with an injection needle and an actuationpusher mounted so as to be able to move in the body, the syringe havinga movable guard for protecting the injection end of the needle, whichguard is able to move with respect to the body between a position inwhich it is retracted in the body away from the injection end of theneedle and an active protection position in which the front end of theguard is at the front of the injection end of the needle, the guard andthe body having associated projecting and recessed reliefs for holdingthe guard in a retracted position.

[0002] A syringe of this type is described for example in the documentFR-A-2.757.066.

[0003] In this document, the movable guard of the injection end of theneedle has legs entering inside the syringe.

[0004] The legs have projections adapted to cooperate with the frontwall of the body of the syringe in order to keep the guard in itsretracted position. The elasticity of the legs of the guard enable theprojections to be left free and thus enable the guard to be released.

[0005] In practice, it is found that, if a very violent push is exertedon the actuation pusher during injection, the pressure exerted on theneedle guard is such that this may be released and move forwards. Theintermediate perforatable piston of the syringe being moved forwards,and it is then no longer possible to inject all the content of thesyringe.

[0006] The aim of the invention is to afford a solution to this problemby in particular limiting the risks of unintentional movement of theneedle guard towards its active protection position during injection.

[0007] To this end, the subject matter of the invention is a syringe ofthe aforementioned type, characterised in that it has a retractablemember for the positive retaining of the engagement of the saidassociated projecting and recessed reliefs, when the guard is in aretracted position, and in that the actuation pusher and the saidretaining member are adapted for a retraction of the said retainingmember with respect to the needle guard, under the action of the pushingin of the actuation pusher into the body, at the end of injection,providing a release of the positive retaining of the engagement of theassociated projecting and recessed reliefs.

[0008] According to particular embodiments, the syringe can have one ormore of the following characteristics:

[0009] the needle guard and the retractable retaining member are made inone piece;

[0010] the retractable retaining member and the needle guard areinitially connected by a breakable link;

[0011] the said associated projecting and recessed reliefs comprise atleast one recess provided in the syringe body and at least one elasticarm carrying an external projection adapted to be received in anassociated recess in the body, and the said retaining member has atleast one stop for holding the external projection or projections in theassociated recess, before retraction of the said retaining member;

[0012] the said elastic arms are provided by the rear end portion of theneedle guard turned towards the rear actuation piston;

[0013] the said injection needle is extended axially inside the body asfar as a rear end, away from which there is initially disposed, in thebody, a perforatable transverse wall, the needle and the said transversewall being able to move with respect to each other from an initialposition in which the transverse wall is distant from the needle as faras a final position in which the transverse wall is pierced by the saidneedle;

[0014] the said retaining member has a passage for the axial guidance ofthe rear end of the needle, when the transverse wall is perforated;

[0015] the said transverse wall is axially deformable under the actionof the actuation pusher acting on the said retaining member;

[0016] the said needle guard and the said transverse wall are initiallyspaced apart from each other, and they have complementary profiles foraxial connection by elastic engagement;

[0017] the needle guard and the transverse wall have axial connectionmeans at least when the needle and the transverse wall are in theirfinal position, and the needle guard and the syringe body havecomplementary projecting and recessed profiles preventing the movementof the needle guard towards the actuation pusher when the needle and thetransverse wall are in their final position;

[0018] the needle guard has at least two legs extending generallyparallel, which legs are made in one piece and connected to each otherat their rear end turned towards the actuation pusher;

[0019] the needle guard has an attached ring connecting the ends of thelegs opposite to their end turned towards the actuation piston;

[0020] the needle guard and the syringe body have complementaryprojecting and recessed profiles preventing the movement of the needleguard towards the actuation pusher when the needle guard is in itsinitial retracted position; and

[0021] the syringe body has at least one elastic blade and the needleguard has at least one notch adapted to cooperate with the said elasticblade in order to prevent the movement of the needle guard towards theactuation pusher when the needle guard is in its active protectionposition.

[0022] The invention will be better understood from a reading of thedescription which follows, given solely by way of example and made withreference to the drawings, in which:

[0023]FIG. 1A is a view in longitudinal section of a syringe accordingto the invention, before use;

[0024]FIG. 1B is a view in longitudinal section of the syringe of FIG.1A in a cutting plane offset angularly by 90°;

[0025]FIG. 1C is a larger-scale view of the rear end of the needle guardin the cutting plane of FIG. 1B;

[0026]FIG. 1D is a larger-scale view of the front end of the needleguard in the cutting plane of FIG. 1B;

[0027]FIG. 2 is a view in perspective and longitudinal section of theneedle support of the syringe according to the invention;

[0028]FIG. 3A is a perspective view of the needle guard of the syringeaccording to the invention before mounting in the syringe;

[0029]FIG. 3B is a view in perspective and longitudinal section of theneedle guard before mounting in the syringe;

[0030]FIGS. 4A, 4B, 4C and 4D are views similar to FIGS. 1A, 1B, 1C and1D respectively after perforation of the intermediate piston;

[0031]FIGS. 5A, 5B, 5C and 5D are views similar to FIGS. 1A, 1B, 1C and1D respectively, at the end of injection, before release of the needleguard;

[0032]FIGS. 6A, 6B, 6C and 6D are views similar to FIGS. 1A, 1B, 1C and1D respectively, after release of the needle guard;

[0033]FIGS. 7A, 7B, 7C and 7D are views similar to FIGS. 1A, 1B, 1C and1D respectively, when the needle guard is put in place;

[0034]FIGS. 8A, 8B, 8C and 8D are views similar to FIGS. 1A, 1B, 1C and1D respectively, at the end of the fitting of the needle guard in itsactive protection position;

[0035]FIG. 9 is a view in longitudinal section of the front end ofanother embodiment of a needle guard used in a syringe according to theinvention;

[0036]FIGS. 10A and 10B are views similar to FIGS. 1A and 1B of avariant embodiment of a syringe according to the invention;

[0037]FIGS. 11A and 11B are views respectively in longitudinal sectionand externally of the actuation pusher of the syringe of FIGS. 10A and10B, this being shown respectively in its retracted state and in itsdeployed state;

[0038]FIG. 11C is a view in cross-section taken along the line XI-XI ofthe actuation pusher of FIG. 11A;

[0039]FIGS. 12A, 12B and 12C are views similar to FIGS. 5A, 5B and 5C ofthe variant embodiment of the syringe;

[0040]FIGS. 13A, 13B, 13C are views similar to FIGS. 6A, 6B and 6C ofthe variant embodiment of the syringe; and

[0041]FIGS. 14A, 14B and 14C are views similar to FIGS. 8A, 8B and 8C ofthe variant embodiment of the syringe.

[0042] The injection syringe 10 depicted in FIG. 1, with an overallshape generated by rotation, of axis X-X, is a single-use syringe. It isoffered ready for use and already containing medical fluid to beinjected. It comprises essentially an elongate syringe body 12 and anactuation pusher 14 mounted so as to be able to move inside the body 12.

[0043] The syringe body 12 is formed by a tube 16, at the front end ofwhich a needle support 18 is fixed. This needle support has a crosspiece20 forming the front wall of the syringe body. This crosspiece 20,visible in FIG. 1B, is provided with an injection needle 22 passingthrough. The latter has a front injection end 22A projecting withrespect to the body 12. The needle is extended axially inside the body12 as far as a rear end 22B.

[0044] The tube 16 is produced for example from glass and has a circularcross-section. Its front end is provided externally with a peripheralrim 24 visible in FIG. 1C. This rim is intended for holding the needlesupport 18. At the rear end of the tube 16 there is attached a grippingmember 25 facilitating the gripping of the syringe body between theindex and middle fingers. This comprises a sleeve 26 snapped externallyon the end of the tube 16 and two diametrically opposed lugs 27 forsupporting the fingers.

[0045] The needle support 18 is shown in section in FIG. 2. It isdelimited externally by a sleeve 28. The crosspiece 20 is made in onepiece with the sleeve 28 in the vicinity of its front end, where itextends along a diameter of the sleeve. On the internal wall of thesleeve 28 there is provided, close to its open end opposite to thecrosspiece 20, a peripheral groove 29 for receiving the rim 24.

[0046] Immediately in front of the peripheral groove 29, on the sameside as the crosspiece 20, two recesses 30 are provided in the internalsurface of the sleeve 28. These recesses 30 have, at their end turnedtowards the crosspiece 20, a ramp 31 providing a progressive reductionin the depth of the recess in the direction of the crosspiece 20, thatis to say towards the front end of the syringe.

[0047] The crosspiece 20 has an axial stud 32 made in one piece, whichholds the injection needle 22. This stud, visible in FIG. 1D, isdirected towards the injection end 22A of the needle and is receivedinside the space delimited by the sleeve 28.

[0048] Two identical passages 34, in the shape of a half-moon, aredelimited on each side of the partition 20 inside the sleeve 28.

[0049] These passages 34 provide guidance for a needle guard 36 shownalone in FIGS. 3A and 3B.

[0050] The needle guard 36 has a generally elongate shape. It has anaxial pipe 38 passing axially right through it. The guard 36 is splitlongitudinally over the main part of its length from its front end andthus delimits two legs 40 extending parallel to each other on each sideof the slit denoted 42. The two legs are connected to each other closeto the rear end of the needle guard by an annulus 46 made in one piece.The two legs 40 and the annulus 46 form the body of the guard. Each ofthe legs is extended by two pillars 48 extending beyond the annulus 46.The pillars 48 are connected opposite the legs 40 by a head 50 generatedby rotation and extending along the axis of the needle guard. This head50 has a generally cylindrical wall 52 delimiting an internal passage54. At its end turned towards the legs 40, the cylindrical wall 52 hasan external collar 56. At its other end, the cylindrical wall 52 isbordered by an external snapping-on rim 58 having a frustoconicalsurface turned towards the end of the head 50, this frustoconicalsurface ending in a shoulder 62 facing the collar 56.

[0051] In the gap 63 delimited between the annulus 46 connecting thelegs and the head 50 there extend two elastic arms 64 connected at oneof their ends to the annulus 46, with which they are made in one piece.These arms are generally rectilinear and have a free end. At rest, theyextend in a plane passing through the axis of the needle guard andseparate progressively from the axis thereof towards their free end.

[0052] At its free end, each arm has an external projection 66 turned inthe opposite direction to the axis of the guard. This projection isadapted to engage in a recess 30 in the needle support.

[0053] In addition, at this same end, each arm 64 has an internalprojection 68 turned towards the axis of the guard.

[0054] A retractable member 70 for the positive holding of the arms 64in a separated position is initially disposed partially between the endsof the arms 64. This holding member has a tubular body 72 extendinginitially inside the pipe 54 along the axis of the guard. The length ofthe tubular body 72 is such that its free end denoted 74 projects beyondthe rear end of the head 70 along the axis of the guard.

[0055] Internally, the tubular body 72 defines a generally frustoconicalpassage 76 for guiding and centring the rear end 22B of the needle.

[0056] At its front end, extending initially between the free ends ofthe arms 64, the holding member 70 has externally two diametricallyopposed protrusions 78. These are adapted to form support stops for theinternal projections 68 thus holding the arms 64 separated and theexternal projections 64 in the recesses 30 in the needle support.

[0057] At its external periphery, the holding member 70 is connected tothe head 50 of the needle guard by a breakable link 80 formed by a webconnecting the holding member and the head 50, the head and the holdingmember being made in one piece with each other through this web at theend of the passage 54.

[0058] As shown in FIG. 1C, before use of the syringe, the rear end 22Bof the needle extends in the passage 76, so that the end of the needleis completely covered by the holding member 70.

[0059] Each leg 40 of the guard has, on its lateral surface, threenotches 81A, 81B, 81C disposed longitudinally in this order, from thefront end of the legs of the guard as far as their rear end where thetwo legs are connected by the annulus 46.

[0060] The notches 81A and 81B are disposed close to each other in theimmediate vicinity of the front end of the legs 40. On the other hand,the notch 81C in each leg is disposed immediately in front of theannulus 46.

[0061] The three notches have identical profiles. As illustrated forexample in FIG. 1D, each notch has an inclined ramp 82 from the lateralsurface of the leg towards the bottom of the notch, in a direction goingfrom the rear of the leg towards the front thereof. This ramp 82 isfollowed, towards the front of each leg, by a shoulder 83 forming astop.

[0062] The notches 81A, 81B and 81C constitute recessed reliefs adaptedto cooperate with associated projecting reliefs provided on the needlesupport 28 in order to prevent rearward return of the needle guard fromthree positions corresponding to each of the notches.

[0063] The complementary projecting profiles carried by the needle guard28 are formed by elastic blades 84 made in one piece with the sleeve 28of the needle support. These elastic blades project with respect to theinternal lateral surface of the sleeve.

[0064] The elastic blades 84 are connected to the sleeve 28 only attheir rear end. They extend generally parallel to the axis of thesyringe and their free end is turned towards the injection end 22A ofthe needle. Each elastic blade has an elbow 85 extended by a projectinglocking portion 86 turned towards the axis of the syringe. Thisprojecting locking portion 86 is adapted to be received successively ineach of the notches 81A, 81B. In particular, the end of the lockingportion 86 is adapted to come into abutment against the shoulder 83 ofeach of these notches and to slide on the ramps 82 in order to cause anelastic deformation of the associated blade.

[0065] The actuation pusher 14 has a piston rod 87 with a cruciformcross-section and having, at its rear end, a pad 87A for supporting thethumb of the operator. At its opposite end the piston rod 87 has agenerally frustoconical axial protuberance 88 whose diameter decreasestowards its free end. The maximum diameter of this protuberance is lessthan the cross-section of the passage 54 provided in the head of theguard. A housing 89 open on the front is provided axially in the pistonrod 87.

[0066] This housing serves for receiving the rear end 22B of the needleat the end of injection. The housing 89 has an elongate shape along theaxis X-X and a circular cross-section.

[0067] The housing 89 is closed off by an end piston 90 in the form of abowl forming a rear piston of the syringe. This piston 90 has acylindrical side wall 91A closed off by a disc 91B forming the bottom ofthe bowl. The side wall 91A is provided on the inside with successiverims. On its external surface, the piston rod 87 has annular grooves inwhich the successive rims are received, thus providing an axialconnection of the rear piston 90 and piston rod 87. The rear piston 90is elastically deformable, notably in its part consisting of the disc91B. The rear piston 90 constitutes a transverse wall adapted to slidesealingly inside the tube 16. The disc 91A can be perforated in itscentral part.

[0068] As depicted in FIG. 1A, the fluid to be injected 92 is disposedinside the tube 16 in a space delimited by the rear piston 90 and anintermediate piston 94.

[0069] The intermediate piston 94 is shown to a larger scale in FIG. 1C.It is produced from a resilient material such as rubber. It has atransverse wall 96 which can be perforated axially in its centralregion. This transverse wall is surrounded by a lateral sleeve 98 madein one piece with it. This lateral sleeve is adapted to be pressedsealingly against the internal surface of the tube 19. At its end turnedtowards the head 50 of the needle guard, the side wall 98 and thetransverse wall 96 delimit, in the intermediate piston 94, a chamber 100having a shape complementary to the external profile of the head 50delimited by the lateral surface 52 and the snapping-on rim 58. Thechamber 100 opens towards the needle guard. It has, at the periphery ofits opening, a radially projecting edge 101, adapted to provide thesubsequent holding of the head 50 in the chamber.

[0070] Thus the chamber 100 is adapted to receive the end of the head 50and to hold it axially by elastic snapping on.

[0071] At the bottom of the chamber 100, the transverse wall 96 has aplane surface 102 turned towards the holding member 70. This surface 102is adapted to bear along the edge of the body of the holding member 70from its end 74 projecting with respect to the head 50 of the needleguard.

[0072] The surface 102 is formed at the top of a protrusion 104 providedat the bottom of the chamber 100, this protrusion being surrounded by anannular channel. The area of the plane surface 102 is less than thecross-section of the pipe 54 across which the holding member 70 ismounted.

[0073] Along its face turned towards the actuating pusher 14, theintermediate piston 94 has, at its centre, a well 106, whose peripheryis connected to the side wall 98 by a frustoconical surface 108 splayingprogressively in the direction of the actuation pusher 14.

[0074] This frustoconical surface 108 constitutes an abutment seat forthe end of the actuation pusher 14.

[0075] As illustrated in FIG. 1C, the intermediate piston 94 is disposedinitially immediately behind the rear end of the needle guard 36. Inparticular, the head 50 of the guard is outside the chamber 100. In thisinitial position, the rear end 22B of the needle is away from theperforatable transverse wall 96.

[0076] In a variant, the intermediate piston 94 is initially engagedaround the head 50 of the guard. The rear end 22B of the needle ishowever away from the perforatable wall 96, this end being disposed inthe passage 76.

[0077] In addition, a cap 110 for guarding the needle 22 is engagedaround the sleeve 28 of the needle support and covers the injection end22A of the needle.

[0078] As illustrated in FIG. 1D, the cap 110 has, at its open end, askirt 120 delimiting an annular space inside which the end of the needlesupport 18 is received.

[0079] The external lateral surface of the needle support 18 and theinternal lateral surface of the skirt 120 are pressed against eachother.

[0080] One of these surfaces advantageously has a helical channel 122opening out, at one end, outside the syringe, when the cap is fitted onthe needle support 18, the other end of the channel 122 opening outinside the cap.

[0081] This helical channel 122 is produced in the skirt 120 in theembodiment envisaged. It provides the circulation of gases between theoutside and inside of the needle guard when this is in place on theneedle support. Thus this channel makes it possible to sterilise thesyringe equipped with its needle guard in an autoclave or any othersterilisation device.

[0082] The syringe is assembled in the following manner.

[0083] The needle 22 is bonded through the needle support 18. The guard36 is introduced into the needle support 18 through its rear end, thatis to say on the same side as the end 22B of the needle. The guard 36 ismounted through the needle support 18 by engaging the legs 40 in thepassages 34 surrounding the stud 32. The legs then extend along the rearpart of the needle 22. In this position, the projecting ends 86 of theelastic blades 84 are received in the notches 81A, preventing removal ofthe guard by traction from its rear end. The front cap 110 is then putin place by fitting it around the sleeve 28.

[0084] The needle support 18, thus provided with the cap 110 and theneedle guard 36, can be manipulated without any risk of degradation tothe ends of the needle, this being protected at both ends. Inparticular, it can be distributed on production lines in vibratingbowls.

[0085] In parallel to the assembly of the needle support, the tube 16 isprovided with the gripping member 25. It is filled with the fluid 92disposed between the intermediate piston 94 and the actuation pusher 14.The needle support 18 is put in place by snapping on the front end ofthe tube 16, as shown in FIG. 1C.

[0086] In order to proceed with the injection, the operator removes thecap 110. In a conventional manner, the operator then exerts a push onthe actuation pusher 14 with his thumb whilst bearing under the lugs 27with the index and middle fingers.

[0087] The pressure thus exerted, transmitted by means of the liquid 92to the intermediate piston 94, causes the latter to move towards therear end 22B of the needle.

[0088] The piston 94 then engages on the head 50 of the needle guard andis held thereon by elastic engagement of the re-entrant edge 101bordering the opening of the chamber at the rear of the snapping-on rim58 of the head.

[0089] In this position, the flat surface 102 provided at the bottom ofthe chamber bears on the rear end of the retractable holding member 70,as illustrated in FIG. 4C.

[0090] The subsequent movement of the piston 94 associated with theneedle guard results in the piston 94 impaling itself on the rear end22B of the needle. In particular, the wall 96 of the intermediate pistonis perforated during its movement.

[0091] When the transverse wall 96 is perforated by the rear end 22B ofthe needle, the conduit 76 passing right through the holding member 70ensures holding of the needle exactly along the axis of the syringe,thus guaranteeing that the perforation of the wall takes place at itsmiddle and exactly in the direction of the axis of the syringe.

[0092] Easy subsequent movement of the piston 94 over the entireinternal portion of the needle 22 is thus guaranteed.

[0093] The continuation of the pushing in of the actuation pusher 14causes the forward movement of the needle guard 36 coupled to theintermediate piston 94. This movement takes place until the externalprojections 66 bear against the ramp 31 formed at the front of eachrecess 30. In this position, illustrated in FIGS. 4A, 4B and 4C, themovement of the needle guard is interrupted, by the abutment of theexternal projections 66 against the ramp 31. This is because, because ofthe presence of the protrusions 78 interposed between the free ends ofthe arms 64, these cannot deform elastically and move closer together,so that the external projections 66 are trapped in the recesses 30, thuspreventing a subsequent axial movement of the needle guard 36.

[0094] In this position, and as illustrated in FIG. 4D, the projectingportions 86 of the elastic blades 84 are received in the recesses 81B,preventing rearward movement of the needle guard.

[0095] The needle guard is then immobilised axially in both directions.This immobilisation is very reliable since on the one hand the specialshape of the blades 84 and of the notches 81B prevents rearward returnof the guard and on the other hand the protrusions 78 ensure positiveholding of the projections 66 in the recesses 30.

[0096] After purging of the syringe, the injection end 22A of the needleis inserted into the tissues of the patient.

[0097] After insertion of the needle, it is possible to carry out a“vein test”, that is to say suction of a drop of blood through theneedle by pulling on the actuation pusher 14. Such a test creates norisk of movement of the intermediate piston 94, this being held by theneedle guard 36 which is itself immobilised by the elastic blades 84engaged in the notches 81B.

[0098] After completion of the test, the fluid 92 is then injectedthrough the needle 22 under the action of the thrust of the actuationpusher 14 pressed in as far as the position depicted in FIGS. 5A, 5B, 5Cand 5D. In this position, most of the fluid 92 is injected and the rearpiston 90 comes into contact with the rear surface of the intermediatepiston 94.

[0099] Throughout the injection, the needle guard 36 is kept immobilethrough the engagement of the projecting portions 86 of the elasticblades in the notches 81B and through the holding of the externalprojections 66 in the recesses 30, this holding being guaranteed by theprotrusions 84 on the retractable holding member 70.

[0100] The holding of the guard is achieved in a reliable mannerwhatever the force applied to the pusher 14 because of the positivelocking of the guard provided by the holding member 70.

[0101] At the end of the injection phase, the rear piston 40 comes intoabutment against the intermediate piston 94, which is carried by theneedle guard which is immobilised axially by the abutment of theexternal projections 86 against the ramps 31.

[0102] When the pressing in of the actuation pusher 14 is continued, andas illustrated in FIGS. 6A, 6B, 6C and 6D, the frustoconical end 88 ofthe piston rod causes an elastic deformation of the transverse disc 91Bof the rear piston 90. This presses on the seat 108 formed on theintermediate piston 94. Under the action of the thrust exerted by thepiston rod 87 through the rear piston 90, the intermediate piston 94deforms by compressing axially. This deformation thus causes a forwardmovement of the transverse wall 96 and in particular of the surface 102in abutment on the end 74 of the retractable holding member 70. Underthe action of this thrust, the holding member 70 is detached from thehead 50 of the needle guard, the breakable connection 80 being brokenunder the effect of the thrust force.

[0103] Under these conditions, the holding member 70 thus disconnectedfrom the remainder of the needle guard 36 moves axially towards aretracted position in the direction of the front end 22A of the needle.In particular, the protrusions 78 initially forming a wedge between theinternal projections 68 are moved in front of these projections, thusfreeing the movement of the free ends of the arms 64.

[0104] As illustrated in FIG. 6C, when the piston rod 87 moves, the arms64, freed from the holding member 70, are deformed elastically under theaction of the cooperation of the external projections 66 with the ramps31 which form cam surfaces.

[0105] The needle guard 36 is then free to move axially towards theinjection end of the needle under the action of the thrust exerted bythe actuation pusher 14.

[0106] When the pushing in of the pusher 14 is continued, and asillustrated in FIGS. 7A, 7B, 7C and 7D, the legs 40 of the needle guardmove progressively along the portion of the needle projecting out of theneedle support 18.

[0107] When the needle guard 36 moves, the rear end 22B of the needleenters inside the chamber 89 after having perforated the rear piston 90.

[0108] The movement of the needle guard 36 takes place under the actionof the pusher 14 until the needle guard comes into contact with thecrosspiece 20, as illustrated in FIGS. 8A, 8B and 8C. In this position,and as illustrated in FIG. 8D, the ends of the elastic blades 84 arereceived between the notches 81C, thus ensuring axial locking of theneedle guard, preventing its rearward return.

[0109] When the needle guard is in its active guarding position, asillustrated in FIGS. 8A and 8B, the front end of the needle guardextends in front of the front end 22A of the injection needle,preventing any risk of pricking from the end of the needle.

[0110]FIG. 9 depicts a variant embodiment of a needle guard used in asyringe as described in the previous figures.

[0111] In this embodiment, the free ends of the legs 80 are equippedwith a ring 130 attached by snapping on or any other appropriateconnection means. This ring provides a securing and connection of thefree ends of the legs. It prevents any risk of seeing the legs of theneedle guard separated whilst the latter is in its active position ofguarding the needle. FIGS. 10 to 13 illustrate another variantembodiment of a syringe according to the invention.

[0112] This embodiment differs solely from the previous embodiment inthat the actuation pusher 14 is replaced by a telescopic actuationpusher 214.

[0113] The telescopic pusher 214 has a piston rod 218 with a front endon which an end piston is mounted, in the form of a bowl 220 similar tothe rear piston 90 of the first embodiment.

[0114] As illustrated in FIGS. 11A, 11B and 11C, the piston rod 218 hasan external tube 222 and an internal rod 224 mounted so as to be able tomove slidably inside the tube 222.

[0115] The external tube 222 has an outside diameter very slightly lessthan the inside diameter of the body of the syringe, that is to say thanthe diameter of the tube 16 and the cross-section of flow through thegripping member 25. At its front end, the tube 222 has a collar 226axially extending the tube. On the external surface of the collar thereis provided a thread 228 for attachment of the end piston 222.

[0116] The tube 222 delimits internally a pipe 230 inside which there isslidably mounted the internal rod 224. The pipe 230 opens out at bothends.

[0117] The pipe 230 has, in cross-section, generally the shape of across, as illustrated in FIG. 11C.

[0118] At its front end, the pipe 230 has a shoulder 232 beyond whichthe collar 226 extends.

[0119] In the vicinity of its rear end, the tube 222 has two oblongapertures 234 able to receive radial protrusions on the rod 224.

[0120] The internal rod 224 has a body 236 with a cross-sectiongenerally in a cross complementary to that of the pipe 230 in order toprovide axial guiding and rotational holding of the rod 224 in the pipe230.

[0121] At its front end, the body 236 of the rod is extended by atubular portion 238 engaged through the collar 226. The length of thetubular portion 238 is greater than the length of the collar 226.Initially, that is to say in the position in FIGS. 11A and 11B, thetubular portion 238 is completely retracted in the collar 226 and thepipe 230.

[0122] The tubular portion 238 internally delimits a housing 239 forreceiving the rear end of the needle. This housing is extended insidethe body 236 of the rod.

[0123] At its rear end, the rod 224 has a pad 240 for supporting thethumb of the user.

[0124] According to the invention, means 242 for the temporary axialconnection of the rod 224 with respect to the tube 222 are provided inthe actuation pusher.

[0125] More precisely, these temporary connection means comprise twoelastic legs 224 made in one piece with the internal rod 224.

[0126] These legs are connected from their rear end to the body 236 ofthe rod. They each have a free end 246 turned towards the front of theactuation pusher. The legs 244 are formed so that, by elasticity, theirfree ends 246 tend to move away from the axis of the rod 224. These freeends 246 are adapted to come into abutment axially on shoulders 248defined in the thickness of the tube 222 in front of the apertures 234in order to provide the axial immobilisation of the internal rod withrespect to the tube.

[0127] On their external surface, the legs 244 have protuberances 250engaged through the apertures 234 and projecting with respect to thelateral surface of the tube 222. These protuberances 250 have, in thedirection of the axis of the pusher, a height progressively increasingfrom the front towards the rear, thus forming a convex cam surfacemoving away progressively from the axis of the pusher from front torear.

[0128] Housings 252 are provided in the body 236 of the internal rod inline with the legs 244 to allow their partial retraction inside the tube222 when they are close to the axis of the internal rod.

[0129] The position of the apertures 234, and the position of theprotuberances 250 on the legs 244, are chosen so that, at the end ofinjection, whilst the actuation pusher is in abutment against the frontpiston 94, the protuberances 250 come into contact with the rear end ofthe syringe body, and more particularly with the rear end of thegripping member 25.

[0130] In order to carry out an injection with such a syringe, the samesteps as those described with regard to FIGS. 1A, 1B and 4A, 4B arefirst of all implemented. During the injection stage, the two slidingelements of the telescopic pusher are kept connected axially because ofthe abutment of the free ends 246 of the legs on the shoulders formingstops 248 provided in the external tube 222. Thus the thrust applied tothe pad 240 is transmitted to the tube 222, which pushes the rear piston220.

[0131] As illustrated in FIGS. 12A and 12B, whilst the rear piston 220is in contact with the front piston 94, as illustrated in FIG. 12C, theprotuberances 250 provided on the elastic legs 244 of the rod are pushedtowards the inside of the tube 222 by cam effect by coming into contactwith the abutment finger 27. The legs 224 are thus deformed, so thattheir free ends 246 are released from the shoulders 248 and are pushedinto the housing 252. The free ends 246 are then retracted in line withthe body 236 of the rod.

[0132] The ends 246 of the legs being separated from the stops 248, theaxial movement of the rod 224 with respect to the tube 222 is madepossible, the axial connection means 242 being released.

[0133] When the pressing on the pad 240 is continued, the thrust is nolonger transmitted to the tube 220, which is kept immobile in abutmentagainst the front piston 94. On the other hand, the rod 224 movesaxially inside the tube 222. Under the effect of this movement, thetubular portion 238 projects progressively beyond the collar 226.

[0134] As illustrated in FIGS. 13A, 13B and 13C, the forward movement ofthe tubular portion 238 causes a deformation of the rear piston 220. Theprojecting part of the tubular portion 238 acts axially on the holdingmember 70 by bearing on its rear end 74. As explained with regard toFIG. 6C, the holding member 70 is disconnected from the needle guard andmoves axially towards a retracted position. Thus the free ends of thearms 64 are released, so that the needle guard can be moved forwards.

[0135] Continuing the pressing on the pad 240 causes the movement of theassembly consisting of the actuation pusher 214 and the needle guarduntil the front and rear pistons are in the front part of the syringebody, as illustrated in FIGS. 14A, 14B and 14C.

[0136] It will be understood that the use of a telescopic pusher, thetwo movable parts of which are initially axially connected, these twoparts being released at the end of the injection phase, avoids having toprecisely size the fixed axial protuberance 88 provided at the end ofthe pusher of the first embodiment. This is because the length of thisprotuberance must be adjusted precisely in order not to be too long,which may occasion lateral leaks around the piston 90, and not to be tooshort, which may make it difficult or impossible to move the holdingmember 70.

[0137] In addition, use of the telescopic pusher reduces the forcenecessary for the movement of the holding member 70. This is because thetelescopic pusher 214 acts only the central part of the piston 94 bymeans of the tubular portion 238 able to move with respect to the tube222. On the other hand, in the first embodiment, the pusher bears on theentire transverse surface of the piston 94. The force necessary for itsdeformation is therefore high.

1. Injection syringe having a syringe body (12) provided with aninjection needle (22) and an actuation pusher (14; 214) mounted so as tobe able to move in the body (12), the syringe having a movable guard(36) for protecting the injection end (22A) of the needle, which guard(36) is able to move with respect to the body (12) between a position inwhich it is retracted in the body (12) away from the injection end ofthe needle and an active protection position in which the front end ofthe guard (36) is at the front of the injection end (22A) of the needle,the guard (36) and the body (12) having associated projecting andrecessed reliefs (30, 66) for holding the guard in a retracted position,characterised in that it has a retractable member (70) for the positiveretaining of the engagement of the said associated projecting andrecessed reliefs (30, 66), when the guard (36) is in a retractedposition, and in that the actuation pusher (14) and the said retainingmember (70) are adapted for a retraction of the said retaining member(70) with respect to the needle guard (36), under the action of thepushing in of the actuation pusher (14; 214) into the body, at the endof injection, providing a release of the positive retaining of theengagement of the associated projecting and recessed reliefs (30, 66).2. Syringe according to claim 1, characterised in that the needle guard(36) and the retractable retaining member (70) are made in one piece. 3.Syringe according to claim 1 or 2, characterised in that the retractableretaining member (70) and the needle guard (36) are initially connectedby a breakable link (80).
 4. Syringe according to any one of thepreceding claims, characterised in that the said associated projectingand recessed reliefs (30, 66) comprise at least one recess (30) providedin the syringe body (12) and at least one elastic arm (64) carrying anexternal projection (66) adapted to be received in an associated recess(30) in the body, and the said retaining member (70) has at least onestop (78) for holding the external projection or projections (66) in theassociated recess (30), before retraction of the said retaining member(70).
 5. Syringe according to claim 4, characterised in that the saidelastic arms (64) are provided by the rear end portion of the needleguard turned towards the rear actuation piston (14).
 6. Syringeaccording to any one of the preceding claims, characterised in that thesaid injection needle (22) is extended axially inside the body (12) asfar as a rear end (22B), away from which there is initially disposed, inthe body, a perforatable transverse wall (94), the needle (22) and thesaid transverse wall (94) being able to move with respect to each otherfrom an initial position in which the transverse wall (94) is distantfrom the needle (22) as far as a final position in which the transversewall (94) is pierced by the said needle (22).
 7. Syringe according toclaim 6, characterised in that the said retaining member (70) has apassage (76) for the axial guidance of the rear end of the needle (22B),when the transverse wall (94) is perforated.
 8. Syringe according toclaim 6 or 7, characterised in that the said transverse wall (94) isaxially deformable under the action of the actuation pusher (14) actingon the said retaining member (70).
 9. Syringe according to any one ofclaims 6 to 8, characterised in that the said needle guard (36) and thesaid transverse wall (94) are initially spaced apart from each other,and in that they have complementary profiles (58, 101) for axialconnection by elastic engagement.
 10. Syringe according to any one ofclaims 6 to 9, characterised in that the needle guard (36) and thetransverse wall (94) have axial connection means (58, 101) at least whenthe needle (22) and the transverse wall are in their final position, andin that the needle guard (36) and the syringe body (12) havecomplementary projecting and recessed profiles (81B, 84) preventing themovement of the needle guard (36) towards the actuation pusher (14) whenthe needle (22) and the transverse wall (94) are in their finalposition.
 11. Syringe according to any one of the preceding claims,characterised in that the needle guard (36) has at least two legs (40)extending generally parallel, which legs (40) are made in one piece andconnected to each other at their rear end turned towards the actuationpusher (14).
 12. Syringe according to claim 11, characterised in thatthe needle guard (36) has an attached ring (130) connecting the ends ofthe legs opposite to their end turned towards the actuation piston. 13.Syringe according to any one of the preceding claims, characterised inthat the needle guard (36) and the syringe body (12) have complementaryprojecting and recessed profiles (81A, 84) preventing the movement ofthe needle guard (36) towards the actuation pusher (14) when the needleguard is in its initial retracted position.
 14. Syringe according to anyone of the preceding claims, characterised in that the syringe body (12)has at least one elastic blade (84) and the needle guard (36) has atleast one notch (81C) adapted to cooperate with the said elastic blade(84) in order to prevent the movement of the needle guard (36) towardsthe actuation pusher (14) when the needle guard (36) is in its activeprotection position.
 15. Injection syringe according to any one of thepreceding claims, characterised in that the needle guard (36) is able tomove with respect to the syringe body (12) under the action of theprogressive pushing in of the actuation pusher (14) in the syringe body(12).
 16. Injection syringe according to any one of the precedingclaims, characterised in that the actuation pusher (214) comprises twotelescopic elements (222, 224) mounted so as to be able to move axiallywith respect to each other and releasable means (242) for the axialconnection of the two elements (222, 224) with respect to each otherduring the injection phase, and in that it has means (250) of releasingthe means (246, 248) of axial connection of the two elements (222, 224)at the end of injection.
 17. Injection syringe according to claim 16,characterised in that the actuation pusher (214) has an external tube(222) and an internal rod (224) able to slide inside the external tube(222), which internal rod (224) has a rear end projecting out of theexternal tube (222) and having an abutment surface (240) for a fingerfor pressing in the actuation pusher (224) into the syringe body (12),and in that the internal rod (224) has an extension (238) able to move,after release of the axial disconnection means (246, 248), between aninjection position in which the said extension (238) is at leastpartially retracted in the external tube (222) and an active position ofretraction of the holding member (70) in which the extension (238)projects with respect to the external tube (222).
 18. Injection syringeaccording to claim 17, characterised in that the releasable axialconnection means (242) have at least one aperture (234) provided in theexternal tube (222) and at least one projecting member (244) connectedto the internal rod (224), the projecting member or members (244) beingelastically engaged in an aperture (234), the aperture or apertureshaving, at one end, a stop (248) for the axial immobilisation of theexternal tube (222) for the abutment of the projection (244) engaged inthe aperture (234).
 19. Injection syringe according to any one of claims16 to 18, characterised in that the means of releasing the means (246,248) of axial connection of the two elements (222, 224) at the end ofinjection have at least one release member (250) able to cooperate withthe syringe body (12) at the end of injection in order to cause therelease of the axial connection means (246, 248).